Web carrier, web carrying method, and web carriage control program

ABSTRACT

Provided is a web carrier which can prevent creasing of a web by detecting a sign of creasing of a web during carriage of the web. The web carrier ( 1 ) for carrying a sheetlike web ( 10 ) by means of a plurality of rollers ( 2 ) detects the linear pattern of a waveform generated on the web ( 10 ) from an image picked up by means of a camera (imaging means) ( 3 ) using an image analysis means ( 73 ) in a controller ( 7 ), recognizes a state becoming the sign of creasing with the aid of the image and simultaneously analyzes the entering direction of the linear pattern into a guide roller ( 2   c ), drives the shaft ( 20   c ) of the guide roller (angle adjusting roller) ( 2   c ) in the direction of canceling the waveform (so that the web is not creased), and controls an alignment adjusting means ( 5 ) such that the web is not creased.

TECHNICAL FIELD

The present invention relates to a web transport apparatus, a webtransporting method and a web transport control program for transportinga sheet web, in which rollers are used for supporting and transportingthe web.

BACKGROUND ART

In the industrial field, a technique of transporting continuous flexiblematerial such as paper, plastic film, metal foil (hereinafter called“web”), using rollers for supporting and transporting the web, which iscalled a web handling, is widely used. These days, the transporttechnique is applied to materials provided with the additional valuesuch as liquid crystal color filter made by coating the liquid crystalon the plastic film. According to the increasing demand for such highvalue-added materials, the transport technique requires high speed, highefficiency and high precision.

Conventionally, various techniques of adjusting a web tension to stablytransport the web are disclosed (see e.g. JP 2003-212406 A, JP2000-143053 A).

For example, a dancer roller disposed between web transporting rollersis moved in the perpendicular direction to the transportation directionto adjust the tension applied to the web by using a pressing apparatus,thereby obtaining the stable transportation of the web without wrinklingand slipping.

However, considering the transporting speed becomes high, theconventional tension control may fail to remove damages such as wrinklesgenerated during transport. These problems are called web defects thatare the technical objective in the industrial field to be solved.

It is thought that the wrinkles are caused by a misalignment, or anon-parallel arrangement of the web transporting rollers, which isadjusted by an operator with his experiences.

In the case that the operator uses the experiences to adjust thearrangement of the rollers, when the wrinkles are generated in the highvalue-added material such as the liquid crystal color filter, thematerial cannot be used, which causes a serious damage. In the casewhere the operator detects a sign of generating wrinkles by theexperience during transporting the web and adjusts the arrangement ofthe rollers, the productivity depends on the operator's ability and thehigh-speed, high-efficiency transporting is not obtained.

The present invention solves the above-mentioned problems and aims toprovide unexpected web transport apparatus, web transporting method andweb transport control program capable of detecting the sign of wrinklingof the web during the web transport and of preventing the generation ofwrinkles.

SUMMARY OF INVENTION

The present invention is to achieve the goal, and the first aspect ofthe present invention is a web transport apparatus which transports asheet web by using multiple rollers and includes a driving roller, anangle adjustable roller, imaging means, alignment adjusting means and acontroller that has image analyzing means and shaft angle control means.

In the advantageous embodiment, the web transport apparatus picks up animage of the web, which is transported on the angle adjustable rollerthat is adjustable in a shaft direction and is disposed adjacentupstream of the driving roller, by means of the imaging means. Theapparatus detects a linear pattern showing a waveform (waving) generatedon the web from the picked up image, and analyzes an entering directionof the linear pattern into the angle adjustable roller. The waveform isa sign of wrinkling.

The apparatus controls the alignment adjusting means such that theentering direction of the linear pattern analyzed by means of the imageanalyzing means is perpendicular to the shaft direction by means of theshaft angle control means. The apparatus adjusts the shaft angle of theangle adjustable roller by means of the alignment control means.

Thus, the apparatus weakens the waveform as the sign of wrinkling beforethe wrinkle is generated and prevents the generation of wrinkles.

In the preferable embodiment of the present invention, the imageanalyzing means detects the linear pattern of the waveform in the imageon the basis of a color or brightness of the image, and determines thedirection of the linear pattern as the entering direction on the basisof a predetermined coordinate system.

In the above structure, when the image analyzing means analyzes thepicked up image, the apparatus detects the linear pattern of thewaveform in the image on the basis of a color or brightness of theimage. The apparatus analyzes the direction of the linear pattern bymeans of the image analyzing means to determine the traveling directionof the waveform on the web.

The web transport apparatus of the present invention further includes adancer roller, tension measuring means, and tension adjusting means, andthe controller further includes critical tension calculating means andtension control means.

The apparatus calculates a critical minimum tension as the criticalvalue in which the web slips and a critical maximum tension as thecritical value in which the web is wrinkled, on the basis of a drivinginformation as to a predetermined driving condition (transportingvelocity etc.) and of physical properties (Young's modulus, Poisson'sratio etc.) of the web by means of the critical tension calculatingmeans.

The apparatus measures the tension applied by the dancer roller thatadjusts the tension on the web by means of the tension measuring means,and moves the dancer roller such that the measured tension is within thecritical minimum tension and the critical maximum tension by means ofthe tension control means.

According to the above-described embodiment, the tension on the web iscontrolled within the range between the critical minimum tension and thecritical maximum tension, thereby preventing wrinkling and slipping.

The second aspect of the present invention is a web transporting methodfor a web transport apparatus provided with multiple rollerstransporting a sheet web which includes a critical tension calculationstep, a tension control step, an image analysis step and a shaft anglecontrol step.

In the critical tension calculation step, a critical minimum tension onthe web in which the web slips and a critical maximum tension on the webin which the web is wrinkled are calculated on the basis of a drivinginformation as to a predetermined driving condition of the web transportapparatus and of a physical property of the web.

In the tension control step, the tension on the web is controlled suchthat the tension is within the critical minimum tension and the criticalmaximum tension.

In the image analysis step, a linear pattern of a waveform generated onthe web is detected from an image picked up in the web being transportedon an angle adjustable roller that is adjustable in a shaft directionand an entering direction of the linear pattern into the shaft of theangle adjustable roller is analyzed.

In the shaft angle control step, shaft of the angle adjustable roller ismoved such that the shaft direction is perpendicular to the enteringdirection of the linear pattern analyzed in the image analysis step.

The third aspect of the present invention is a web transport controlprogram for a web transport apparatus provided with multiple rollerstransporting a sheet web, the program ordering a computer to performfunctions as critical tension calculating means, tension control means,image analyzing means and shaft angle control means.

In the critical tension calculating means, a critical minimum tension onthe web in which the web slips and a critical maximum tension on the webin which the web is wrinkled are calculated on the basis of a drivinginformation as to a predetermined driving condition of the web transportapparatus and of a physical property of the web.

In the tension control means, the tension on the web is controlled suchthat the tension is within the critical minimum tension and the criticalmaximum tension.

In the image analyzing means, a linear pattern of a waveform generatedon the web is detected from an image picked up in the web beingtransported on an angle adjustable roller that is adjustable in a shaftdirection and an entering direction of the linear pattern into the shaftof the angle adjustable roller is analyzed.

In the shaft angle control means, shaft of the angle adjustable rolleris moved such that the shaft direction is perpendicular to the enteringdirection of the linear pattern analyzed in the image analysis step.

According to the web transport apparatus as the first aspect of thepresent invention, when transporting the web, the waveform (waving) asthe sign of generating the wrinkle caused by the misalignment among therollers is detected and the shaft angle (skew angle) of the angleadjustable roller, so that the waveform is dampened. Therefore, due tothe present invention, the generation of the wrinkles on the web can beprevented.

Moreover, according to the present invention, the image analyzing meansdetects the waving, which is dampened, so that there is no need toadjust the arrangement of the rollers by the operator. Thus, theproductivity of the web is improved.

Furthermore, according to the present invention, the waveform (waving)generated on the web is detected as the linear pattern in the picked upimage of the web, so that the entering direction of the waveform intothe angle adjustable roller is determined and the shaft of the angleadjustable roller is accurately moved toward the direction of cancelingthe waveform.

According to the present invention, in the web transport, the waveform(waving) as the sign of generating the wrinkle caused by themisalignment among the rollers is detected and the shaft angle (skewangle) of the angle adjustable roller, so that the waveform is dampened.Furthermore, according to the present invention, the tension on the webis controlled within the range between the critical minimum tension asthe critical value in which the web slips and the critical maximumtension as the critical value in which the web is wrinkled, therebypreventing wrinkling and slipping.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a mechanism for generation of wrinkles in the web.

FIG. 2 is a graph showing a condition for preventing the wrinkles andobtaining the stable web transport.

FIG. 3 depicts a side view of the web transport apparatus according tothe present invention.

FIG. 4 depicts a top view of the web transport apparatus according tothe present invention.

FIG. 5 is a block diagram of a controller installed in the web transportapparatus.

FIG. 6 shows the situation that the wrinkle is generated on the webpassing through a guide roller, (a) depicts the non-wrinkle situation,(b) depicts the situation where a waveform as the sign of wrinklesoccurs, and (c) depicts the situation where the wrinkle is generated.

FIG. 7 shows a control method as to the guide roller when the waveformas the sign of wrinkles (waving) appears on the web.

FIG. 8 depicts a side view of the other web transport apparatusaccording to the present invention.

FIG. 9 is a flowchart of an operation of the web transport apparatusaccording to the present invention.

THE BEST MODE FOR CARRYING OUT THE INVENTION

The best mode for carrying out the present invention (the embodiment) isdescribed below, referring attached drawings. Here, an outline regardinga wrinkle generation mechanism on the web explicated by the inventor isfirstly explained, and the structure and operation of the web transportapparatus that transports the web without generating the wrinkles areexplained in order.

[Wrinkle Generation Mechanism During Web Transport]

Referring to FIG. 1, the wrinkle generation mechanism on the web isexplained. FIG. 1 shows the mechanism for wrinkling, (a) is aperspective view illustrating the relationship between two rollers andthe web, (b) depicts the side view, and (c) depicts the top view. InFIG. 1, the web 10 is transported on two rollers 2 (2 ₁, 2 ₂). The web10 (shown as a transparency) is transported from the upstream roller 2 ₁to the downstream roller 2 ₂.

(Condition for Generating Wrinkle)

The condition that the wrinkle is generated in the web 10 duringtransportation of the web 10 is explained.

When the rollers 2 ₁, 2 ₂ are disposed parallelly, no wrinkles occur onthe web 10. However, if the roller 2 ₂ skews against the roller 2 ₁ andthe misalignment within the roller 2 ₁ and roller 2 ₂ occurs, a shearforce S_(F) due to the bending moment is caused in the web 10 on thetangent line of the roller 2 ₂. Assuming the web 10 is a thin beam fixedto the roller 2 ₁, the web 10 is affected by the shear force S_(F) andbends in the surface. When the shear stress becomes over the criticalbuckling stress of the web 10 regarded as a plate, a buckling B_(L)starts to occur at the center of the web 10 approaching the roller 2 ₂,which is the generating point of wrinkle.

The wrinkle is generated when a skew angle θ of the roller 2 ₂ becomesmore than a critical misalignment angle θ_(cr) represented by Formula(1):

$\begin{matrix}{\theta_{cr} = {\frac{6a^{2}}{E_{x}L^{2}}\sqrt{\sigma_{zcr}^{2} - {\sigma_{zcr}\sigma_{x}}}}} & (1)\end{matrix}$

where a is a roller span [m], L is a web width [m], E_(x) is a Young'smodulus of the web in transportation direction [Pa], σ_(x) is a tensilestress in the transportation direction [Pa], and σ_(zcr) is a criticalbuckling stress [Pa].

The tensile stress σ_(x) is represented by Formula (2):

$\begin{matrix}{\sigma_{x} = \frac{T}{t_{f}}} & (2)\end{matrix}$

where T is a web tension [N/m], and t_(F) is a web thickness [m].

The critical buckling stress σ_(zcr) is represented by Formula (3):

$\begin{matrix}{\sigma_{zcr} = {\frac{L^{2}}{i^{2}a^{2}}\left\{ {{\sigma_{e}\left( {1 + {\zeta_{1}i^{4}\frac{a^{4}}{L^{4}}} + {\zeta_{2}i^{2}\frac{a^{2}}{L^{2}}}} \right)} - \sigma_{x}} \right\}}} & (3)\end{matrix}$

where the σ_(e), ζ₁, ζ₂ are given as Formula (4).

The integer i in the formula (3) is determined by the following relationgiven in Formula (5).

$\begin{matrix}{{\sigma_{e} = \frac{\pi^{2}D_{xx}}{a^{2}t_{f}}},{D_{xx} = \frac{E_{x}t_{f}^{3}}{12\left( {1 - {v_{x}v_{z}}} \right)}},{\zeta_{1} = \frac{E_{z}}{E_{x}}},{\zeta_{2} = {\frac{4\left( {1 - {v_{x}v_{z}}} \right)}{1 + v_{x} + {\left( {1 + v_{x}} \right)/\zeta_{1}}} + v_{z} + {v_{x}\zeta_{1}}}}} & (4) \\{{\sigma_{e}\left\{ {1 - {{i^{2}\left( {i + 1} \right)}^{2}\zeta_{1}\frac{a^{4}}{L^{4}}}} \right\}} < \sigma_{x} < {\sigma_{e}\left\{ {1 - {\left( {i - 1} \right)^{2}i^{2}\zeta_{1}\frac{a^{4}}{L^{4}}}} \right\}}} & (5)\end{matrix}$

(Condition for Spreading Wrinkle)

The condition that the wrinkle generated in the web 10 spreads along thetransportation direction of the web 10 is explained.

When the web 10 in which the wrinkle is generated passes through theroller 2 ₂, the critical buckling stress of the web 10 wrapped aroundthe roller 2 ₂ is much larger than that of the plate material, so thatin the case that the sufficient friction force F_(F) to sustain thelarge shear stress is not acted between the web 10 and the roller 2 ₂,the buckling of the web 10 on the roller 2 ₂ does not occur and thewrinkle disappears.

On the other hand, when the sufficient friction force F_(F) acts betweenthe web and the roller 2 ₂, the web 10 is buckled over the roller 2 ₂and the wrinkle spreads.

The wrinkle spreads when the tension on the web 10 is greater than acritical maximum tension T_(wik) shown in Formula (6):

$\begin{matrix}{T_{wik} = {\frac{2t_{f}^{2}}{\mu \; L}\sqrt{\frac{E_{x}E_{Z}}{3\left( {1 - {v_{x}v_{z}}} \right)}}}} & (6)\end{matrix}$

where t_(F) is the web thickness [m], μ is a friction coefficientbetween the web and the roller, L is the web width [m], E_(x) is theYoung's modulus of the web in transportation direction [Pa], E_(Z) is aYoung's modulus of the web in width direction [Pa], V_(x) is a Poisson'sratio of the web in transportation direction, and v_(z) is a Poisson'sratio of the web in width direction.

The friction coefficient μ is given as following Formula (7):

$\begin{matrix}{\mu = {\frac{1}{RB}{\int_{{- {RB}}/2}^{{RB}/2}{\mu_{l}{x}}}}} & (7)\end{matrix}$

where R is a roller radius [m], and B is a web wrap angle [rad]. μ_(L)is given as following Formula (8):

$\begin{matrix}{\mu_{l} = \left\{ \begin{matrix}\mu_{c} & \left( {h < \sigma} \right) \\{\frac{\mu_{c}}{2}\left( {3 - \frac{h}{\sigma}} \right)} & \left( {\sigma \leq h \leq {3\sigma}} \right) \\0 & \left( {h > {3\sigma}} \right)\end{matrix} \right.} & (8)\end{matrix}$

where μ_(c) is a border friction coefficient between the web and theroller, h is an air film thickness [m], and σ is a surface roughnessbetween the web and the roller.

The surface roughness σ is a composite value calculated by followingFormula (9), using the surface roughness of the roller σ_(r) and that ofthe web σ_(w).

σ=(σ_(r) ²+σ_(w) ²)^(1/2)  (9)

The air film thickness h is determined by following Formula (10):

$\begin{matrix}{{h = {{0.589{R\left( \frac{6\eta \; U}{T} \right)}^{2/3}} - {\frac{kTB}{\eta \; t_{f}U}\left( {1 + \frac{2x}{RB}} \right)}}}{{{{When}\mspace{14mu} h} < 0},{h = 0}}} & (10)\end{matrix}$

where η is an air film viscosity [Pa·s], T is a web tension [N/m], k isa web permeability [m²], x is a coordinated in the web transportationdirection [m], and U is a web transportation velocity [m/s]. As to thecoordinate x, the coordinate of the start point of winding is set asx=−RB/2, that of the end point of winding is set asx=RB/2(−RB/2≦x≦RB/2). The web transportation velocity U is an addedvalue (U_(r)+U_(w)): where U_(r) is a roller velocity and U_(w) is a webvelocity.

When the tension T on the web 10 is not more than the critical tensionT_(wik) shown in Formula (6), the wrinkle is not generated. While, whenthe tension T is too small, the friction force between the web 10 andthe roller 2 and they are easy to slip, so that the transport of the web10 is difficult.

Thereby, a critical tension (critical minimum tension) T_(slip) of thetension T preventing the slip is calculated.

Generally, the limit of occurring slip is shown as Formula (11):

(e ^(μB)−1)TLR=M _(b)  (11)

here Mb is a known value as bearing torque, and may be regarded as“zero.” From Formula (11), the friction coefficient μ is given asFormula (12).

$\begin{matrix}{\mu = {\frac{1}{B}{\ln \left( {1 + \frac{M_{b}}{TLT}} \right)}}} & (12)\end{matrix}$

The friction coefficient μ is a function of the tension T, and thefriction coefficient μ determining the critical tension T_(slip)satisfies the following relation given in Formula (13).

μ(T _(slip))≅0  (13)

From Formulas (7) and (8), the critical tension T_(slip) satisfiesFormula (14).

μ(T _(slip))=∫_(−RB/2) ^(RB/2)μ_(l)(T _(slip))dx=0  (14)

When the web 10 has gas non-permeability such as film or metal foil, k=0in Formula (10). So, where the air film thickness h is “3σ”, μ_(L) is“zero” from Formula (8). In this case, when k=0 in Formula (10), Formula(15) is obtained.

$\begin{matrix}{h = {{0.589{R\left( \frac{6\eta \; U}{T_{slip}} \right)}^{2/3}} = {3\sigma}}} & (15)\end{matrix}$

The critical minimum tension T_(slip) is given as Formula (16).

$\begin{matrix}{T_{slip} = {0.522\; \eta \; {U\left( \frac{\sigma}{R} \right)}^{{- 3}/2}}} & (16)\end{matrix}$

Note that when the web 10 has gas permeability such as paper or textile,solving Formula (14) by using Newton-Raphson method, the criticaltension T_(slip) is obtained.

The above-described conditions are graphed. FIG. 2 is a graph showing acondition for preventing the wrinkles and transporting the web withstability, and it is the graph of the skew (misalignment) angle of theroller versus the tension on the web.

As shown in FIG. 2, when the tension T is more than the critical minimumtension T_(slip) calculated by Formula (16) and less than the criticalmaximum tension T_(wik) calculated by Formula (6), the web 10 is stablytransported without slipping and wrinkling.

When the tension T is less than the critical minimum tension T_(slip),the slip occurs, and when the tension T is more than the criticalmaximum tension T_(wik), the wrinkle is generated. However, the skewangle θ of the roller 2 ₂ is set less than the critical misalignmentangle θ_(cr) calculated by Formula (1), so that the web 10 is stablytransported without generating wrinkles.

Thus, in the web transport, in order to stably transport the web withoutoccurring slips and generating wrinkles, the tension T on the web 10 andthe skew angle θ of the roller 2 ₂ are maintained in the stable areaS_(T) apart from the slip area S_(L) and the wrinkle area W_(r) in thegraph shown in FIG. 2.

The structure and operation of the web transport apparatus enabled tomaintain the tension T on the web 10 and the skew angle θ of the rollerin the stable area S_(T) is explained below.

[Structure of Web Transport Apparatus]

Referring to FIGS. 3, 4, the web transport apparatus in accordance withthe present invention is explained. FIG. 3 depicts the side view of theweb transport apparatus. FIG. 4 depicts the top view of the webtransport apparatus.

As depicted in FIGS. 3, 4, the web transport apparatus 1 transports theweb 10 composed of continuous flexible material such as paper, plasticfilm, metal foil or the like with the rollers 2 without generatingwrinkles and occurring slips.

The apparatus 1 transports the web 10 from a delivery part 100 to awinding part 101. The apparatus 1 includes the rollers 2, a camera 3,tension adjusting means 4, alignment adjusting means 5, roller drivingmeans 6, and a controller 7.

The rollers 2 rotate around shafts to transport the web 10 from upstreamto downstream. The rollers 2 contains a support roller 2 a, a dancerroller 2 b, a guide roller 2 c, a driving roller 2 d. The shafts ofthese rollers 2 are parallel. Unfortunately, the shafts are not alwaysparallel, so that the skew angle of the guide roller 2 c changes to keepthe parallelity.

The support roller 2 a has a shaft 20 a pivoted to the main body of theapparatus 1 and is configured as a driven roller for transportation ofthe web 10. The support roller 2 a leads the web 10 delivered from thedelivery part 100 to the dancer roller 2 b.

The dancer roller 2 b has a shaft 20 b being adjustable in position andapplies the tension to the web 10. In the dancer roller 2 b, the tensionadjusting means 4 moves the shaft 20 b in the perpendicular direction tothe install surface such that the tension acts on the web 10.

The guide roller (angle control roller) 2 c has a shaft 20 c having oneend fixed to the main body of the apparatus 1 and other end (movableend) adjustable in position. In the guide roller 2 c, the alignmentadjusting means 5 adjusts the other end of the shaft in the horizontaldirection to the install surface so that the parallelity to the shaftsof upstream rollers.

The driving roller 2 d has a shaft 20 d rotated by the roller drivingmeans 6 to generate the friction force within the web 10 and transportthe web 10. The driving roller 2 d transports the web 10 delivered fromthe guide roller 2 c to the winding part 101.

The camera (imaging means) 3 is disposed in the neighborhood of theguide roller 2 c and picks up the image of the web 10. The image pickedup by the camera 3 is transmitted to the controller 7 as an image signalin the frame unit. The image picked up by the camera 3 is analyzed inthe controller 7 to determine whether a waveform as the wrinkle signoccurs in the web 10 or not. The analyzing method is explained laterwith the structure of the controller 7.

The tension adjusting means 4 adjusts the position of the shaft 20 b ofthe roller 2 b to control the tension on the web 10. The tensionadjusting means 4 moves the shaft 20 b of the roller 2 b, on the basisof the drive signal (for tension control), in the perpendiculardirection to the install surface so that the tension applied to the web10 is adjusted. The tension adjusting means 4 may be a hydrauliccylinder, an air cylinder or the like.

In the embodiment, the tension adjusting means 4 adjusts the shaft 20 bof the roller 2 b in the vertical direction, although the movingdirection is not limited and may be the direction in which the tensionon the web 10 can be adjusted in accordance with the roller arrangement.

The tension adjusting means 4 contains a tension sensor 40 measuring thetension on the web 10, and transmits the measured tension to thecontroller 7.

The alignment adjusting means 5 adjusts the skew angle (misalignmentangle) of the shaft 20 c of the guide roller 2 c. In the embodiment, thealignment adjusting means 5 moves the movable end of the shaft 20 c ofthe roller 2 c, on the basis of the drive signal (for alignmentcontrol), in the horizontal direction to the install surface so that theskew angle of the shaft 20 c is adjusted. The alignment adjusting means5 may include a micro screw for adjustment of the movable end of theshaft 20 c or a piezo device deformed in response to electric voltage ormagnetism for adjustment of the movable end of the shaft 20 c.

In the embodiment, the alignment adjusting means 5 adjusts the shaft 20c of the roller 2 c in the horizontal direction, although the movingdirection is not limited and may be the direction in which the enteringdirection of the web 10 into the roller 2 c can be adjusted.

The roller driving means 6 drives the shaft 20 d of the driving roller 2d to rotate, and is, e.g., a normal motor. In the embodiment, the rollerdriving means 6 rotates the shaft 20 d of the roller 2 d on the basis ofthe drive signal (for power supply).

The controller 7 is a control unit for the web transport apparatus 1 andconfigured as a normal computer including a CPU (Central ProcessingUnit), a RAM (Random Access Memory) and the like.

Referring to FIG. 5 (and FIGS. 3, 4), the structure of the controller 7is explained. FIG. 5 is a block diagram of the controller.

The controller 7 includes a memory 70, critical tension calculatingmeans 71, tension control means 72, image analyzing means 73, shaftangle control means 74 and drive control means 75.

The memory 70 memorizes values of physical properties of the web 10,driving information and the like, and is configured as a normal memorysuch as semiconductor memory, hard disc and so forth.

The values of physical properties of the web 10 memorized in the memory70 are the unique values of the web 10 such as Young's modulus,Poisson's ratio, web thickness, web width, and friction coefficientexplained in Formulas (1) through (16).

The driving information memorized in the memory 70 contains conditionvalues for driving the apparatus 1 such as roller radius, web wrapangle, and web transportation velocity explained in Formulas (1) through(16).

The values of physical properties and driving information may bememorized in the memory 70 in advance, or inputted via input means suchas keyboard (not shown).

Further, the memory 70 memorizes the critical values calculated by thecritical tension calculating means 71.

The critical tension calculating means 71 calculates a criticalcondition for preventing wrinkles and slips of the web 10 during thetransportation of the web 10. The means 71 includes critical maximumtension calculating means 71 a and critical minimum tension calculatingmeans 71 b.

The critical maximum tension calculating means 71 a calculates themaximum tension on the web 10, in which the wrinkle is generated in theweb 10. The means 71 a calculates the critical maximum tension T_(wik)explained in Formula (6) on the basis of the physical properties of theweb 10 and driving information memorized in the memory 70. The criticaltension T_(wik) is outputted to the tension control means 72.

The critical minimum tension calculating means 71 b calculates theminimum tension on the web 10, in which the slip is occurred in the web10. The means 71 b calculates the critical minimum tension T_(slip)explained in Formula (16) on the basis of the physical properties of theweb 10 and driving information memorized in the memory 70. The criticalminimum tension T_(slip) is outputted to the tension control means 72.

The tension control means 72 controls the tension on the web 10. Themeans 72 adjusts the position of the shaft 20 b of the dancer roller 2 bto control the tension on the web 10. The means 72 includes initialtension setting means 72 a, measured tension input means 72 b andtension range control means 72 c.

The initial tension setting means 72 a sets the initial tension on theweb 10. The means 72 a sets the initial tension as the tension T₀determined by following Formula (17), on the basis of the criticaltensions T_(wik) and T_(slip) calculated by the critical tensioncalculating means 71. For example, the tension T₀ is set as the averagevalue of the critical maximum tension T_(wik) and critical minimumtension T_(slip).

T_(slip)<T₀<T_(wik)  (17)

The measured tension input means 72 b inputs the tension measured by thetension sensor 40 of the tension adjusting means 4 as the measurementvalue. The measurement value inputted from the means 72 b is transmittedto the tension range control means 72 c.

The tension range control means 72 c controls the dancer roller 2 c suchthat the tension on the web 10 is within the range between the criticaltensions T_(wik) and T_(slip).

The means 72 c outputs the drive signal (for tension control) to thetension adjusting means 4 so that the initial tension set by the initialtension setting means 72 a is the tension on the web 10. Moreover, themeans 72 c outputs the drive signal (for tension control) to the tensionadjusting means 4 so that the tension range inputted from the measuredtension input means 72 b is in the range between the critical tensionsT_(wik) and T_(slip).

The image analyzing means 73 detects the waveform generated on the web10 on the basis of the color or brightness of the image picked up by thecamera 3 and analyzes the direction of the linear pattern as theentering direction of the waveform into the guide roller 2 c using thepredetermined coordinate system. The means 73 includes image input means73 a and waveform detecting means 73 b.

The image input means 73 a inputs the image picked up by the camera 3.The means 73 a inputs the image picked up by the camera 3 in frame unitin time series and outputs to the waveform detecting means 73 b.

The waveform detecting means 73 b analyzes the image inputted from theimage input means 73 a to detect the waveform as the sign of wrinklingof the web 10 and the entering direction of the waveform into the guideroller 2 c.

Referring to FIG. 6, the wrinkle generated in the web 10 and thewaveform as the sign thereof are explained. FIG. 6 shows the situationthat the wrinkle is generated on the web passing through the guideroller, (a) depicts the non-wrinkle situation, (b) depicts the situationwhere the waveform as the sign of wrinkles occurs, and (c) depicts thesituation where the wrinkle is generated. The web 10 shown in FIG. 6 isdepicted with checkered pattern to easily find the wrinkle.

Before the wrinkle is generated as shown in FIG. 6( c), the waveformoccurs on the web 10 (waving) as shown in FIG. 6( b). The waveform growsinto the wrinkle.

While, when the waveform (waving) occurs as shown in FIG. 6( b), toadjust the shaft angle of the guide roller 2 c makes the waveform dampenor disappear. That is because the waveform shown in FIG. 6( b) canreturn due to the elasticity of the web 10.

Referring to FIG. 5 again, the explanation of the structure of thecontroller 7 is continued.

As explained in FIG. 6, when the wrinkle is generated, the waveformappears on the web 10 as the sign. The waveform detecting means 73 banalyzes the image picked up by the camera 3 to detect the waveformshown in FIG. 6( b).

For example, the means 73 b uses Hough transform to detect the linearpattern (linear pattern of the waveform as the sign of wrinkling) in theimage and find the direction of the linear pattern (entering directionof the waveform).

When the image is a color image, the waveform appeared on the web 10 isdetected as the linear pattern by detecting the pixel value belonged tothe predetermined color vector. When the image is monochrome image, thewaveform is detected as the linear pattern on the basis of thedifference in brightness.

The means 73 b uses Hough transform to transform the x-y coordinatesystem into ρ-θ coordinate system and find the inclination of the linearpattern.

The order that the means 73 b detects the waveform and the enteringdirection of the waveform into the guide roller 2 c are inputted to theshaft angle control means 74.

The shaft angle control means 74 controls the skew angle of the guideroller 2 c on the basis of the entering direction of the waveformdetected by the waveform detecting means 73 b. The means 74 outputs thedrive signal (for alignment control) to the alignment adjusting means 5so that the shaft direction of the guide roller 2 c is perpendicular tothe entering direction of the waveform into the roller 2 c.

Referring to FIG. 7, the adjustment direction to the skew angle of theguide roller 2 c is explained. FIG. 7 shows the control method as to theguide roller when the waveform as the sign of wrinkles (waving) appearson the web. In the figure, the images picked up by the camera 3 areshown and the web 10 is transported around the guide roller 2 c from theupper side to lower side in the figure.

FIG. 7( a) depicts the situation that the waveform enters from the rightupper side to the left lower side in the figure. The shaft angle controlmeans 74 adjusts the skew angle to the arrow A direction in which theguide roller 2 c is perpendicular to the entering direction of thewaveform.

FIG. 7( b) depicts the situation that the waveform enters from the leftupper side to the right lower side in the figure. The shaft anglecontrol means 74 adjusts the skew angle to the arrow B direction inwhich the guide roller 2 c is perpendicular to the entering direction ofthe waveform.

Note that in FIG. 7, for facilitating the understanding, the skew angleof the guide roller 2 c is adjusted by the large angle, however the skewangle is gradually adjusted by 1 degree or 2 degrees.

Thus, the waving disappears, thereby preventing the wrinkle.

Referring to FIG. 5 again, the explanation of the structure of thecontroller 7 is continued.

The drive control means 75 outputs the drive signal (for power supply)for ordering the roller driving means 6 for transportation of the web 10at the predetermined velocity so that the driving roller 2 d is driven.The means 75 outputs the drive signal (for power supply) on the basis ofthe web transporting velocity memorized in the memory 70.

The controller 7 may be operated by means of a web transport controlprogram which orders the computer to perform the functions as theabove-described means.

The structure of the web transport apparatus 1 is explained above,although the structure in accordance with the present invention is notlimited to the structure. In the present invention, the guide roller 2 cadjusts the misalignment angle with respect to the adjacent upstreamroller 2 b, so that the wrinkles are prevented from generating in theweb 10. As shown in FIG. 8, a web transport apparatus 1B, for example,includes more number of rollers than the apparatus 1 (see FIG. 3),provided with the multiple guide rollers 2 c and cameras 3, in whicheach guide roller 2 c adjusts the misalignment angle with respect to theadjacent upstream roller.

[Operation of Web Transport Apparatus]

Referring to FIG. 9 (and FIGS. 3, 4, 5), the operation of the webtransport apparatus 1 is explained. FIG. 9 is a flowchart of theoperation of the web transport apparatus in accordance with the presentinvention. In the explanation, the operation of the apparatus 1 isexplained with priority given to the controller 7.

(Critical Tension Calculation Step)

The apparatus 1 calculates the maximum tension (critical maximum tensionT_(wik)) on the web 10 in which the wrinkle is generated in the web 10by means of the critical maximum tension calculating means 71 a of thecritical tension calculating means 71 (Step S1). The apparatus 1calculates the minimum tension (critical minimum tension T_(slip)) onthe web 10 in which the slip occurs in the web 10 by means of thecritical minimum tension calculating means 71 b of the critical tensioncalculating means 71 (Step S2).

The apparatus 1 sets the initial tension (tension T₀) within the rangebetween the critical tensions T_(wik) and T_(slip) by means of theinitial tension setting means 72 a of the tension control means 72 (StepS3).

The apparatus 1 controls the dancer roller 2 b such that the tension onthe web 10 is the tension set in the step S3 by means of the tensionrange control means 72 c of the tension control means 72 (Step S4).

Due to the above operation, the apparatus 1 initializes the tension.

The apparatus 1 outputs the drive signal from the drive control means 75to the roller driving means 6 to rotate the driving roller 2 d fortransportation of the web 10 (Step S5). The apparatus 1 carries out thefollowing steps: a tension control step, an image analysis step andshaft angle control step.

Here, when received the order to stop the operation (“Yes” in Step S6),the apparatus 1 stops. On the other hand, when there is no order to stopthe operation (“No” in Step S6), the operation proceeds to Step S7.

(Tension Control Step)

The apparatus 1 inputs the tension T on the web 10 measured by thetension sensor 40 of the tension adjusting means 4 by means of themeasured tension input means 72 b of the tension control means 72 (StepS7).

The apparatus 1 outputs the drive signal to the tension adjusting means4 such that the tension T on the web 10 is in the range between thecritical maximum tension T_(wik) calculated in the Step S1 and thecritical minimum tension T_(slip) calculated in the Step S2, andcontrols the vertical position of the dancer roller 2 b (Step S8).

Due to the above operation, the web 10 is transported in the stable areaS_(T) that is the range between the critical tensions T_(wik) andT_(slip) as depicted in FIG. 2; therefore the wrinkles and slips in theweb 10 are prevented from generating.

Note that, according to the physical properties of the web 10, there isthe case where the range between the critical tensions T_(wik) andT_(slip) is narrow, in which it is difficult to control the tensionwithin the range between the critical tensions T_(wik) and T_(slip).

So, the apparatus 1 controls the misalignment angle (skew angle) of theguide roller 2 c to prevent wrinkles.

(Image Analysis Step)

The apparatus 1 inputs the image of the web 10 transported on the guideroller 2 c picked up by the camera 3 in a frame unit in time series bymeans of the image input means 73 a of the image analyzing means 73(Step S9).

The apparatus 1 analyzes the image inputted in the Step S9 to detect thewaveform as the sign of wrinkles (waving) and the entering direction ofthe linear pattern of the waveform into the guide roller 2 c by means ofthe waveform detecting means 73 b (Step 10).

The apparatus 1 determines whether the linear pattern of the waveform isdetected by the means 73 b or not (Step S11).

(Shaft Angle Control Step)

When the linear pattern of the waveform is detected in the Step S11(“Yes”), the apparatus 1 inputs the drive signal to the alignmentadjusting means 5 to pivot the shaft 20 c such that the enteringdirection of the waveform (linear pattern) detected in the Step S10 isperpendicular to the shaft 20 c of the guide roller 2 c by means of theshaft angle control means 74 for control of the skew angle of the guideroller 2 c (Step S12).

Thus, if the operating condition is in the wrinkle area W_(r), the skewangle of the guide roller 2 c is controlled, so that the conditionreturns to the stable area S_(T), and the generation of wrinkles isprevented.

After the Step S12 or when there is no detection of the waveform in theStep S11 (“No”), the apparatus 1 returns to the Step S6 and continuesthe operation.

Due to the above operation, the apparatus 1 transports the web 10without wrinkling and slipping.

Note that, in the embodiment, the tension control step is followed bythe image analysis step and shaft angle control step, although the orderof these operations may be reversed. Moreover, these operations may beperformed parallelly. In the critical tension calculation step, the StepS1 and Step S2 may be reversed or performed parallelly.

INDUSTRIAL APPLICABILITY

The web transport apparatus, web transporting method and web transportcontrol program according to the present invention are applicable to thetechnique of transporting the sheet web supported by the multiplerollers.

1. A web transport apparatus transporting a sheet web by using multiplerollers, comprising: a driving roller transporting the web; an angleadjustable roller disposed adjacent upstream of the driving roller in atransportation direction, provided with a shaft adjustable in a shaftdirection; imaging means for picking up an image of the web transportedon the angle adjustable roller; alignment adjusting means for adjustingthe angle of the shaft of the angle adjustable roller; and a controller,wherein the controller comprising: image analyzing means for finding alinear pattern of a waveform as a sign of wrinkling generated on the webfrom the image picked up by the imaging means; and shaft angle controlmeans for controlling the alignment adjusting means, whereby the web isnot wrinkled.
 2. A web transport apparatus transporting a sheet web byusing multiple rollers, comprising: a driving roller transporting theweb; an angle adjustable roller disposed adjacent upstream of thedriving roller in a transportation direction, provided with a shaftadjustable in a shaft direction; imaging means for picking up an imageof the web transported on the angle adjustable roller; alignmentadjusting means for adjusting the angle of the shaft of the angleadjustable roller; and a controller, wherein the controller comprising:image analyzing means for detecting a linear pattern of a waveformgenerated on the web to find a sign of wrinkling in the web from theimage picked up by the imaging means, and for analyzing an enteringdirection of the linear pattern into the angle adjustable roller; andshaft angle control means for adjusting the shaft of the angleadjustable roller such that the shaft direction is perpendicular to theentering direction of the linear pattern analyzed by means of the imageanalyzing means, and for controlling the alignment adjusting means,whereby the web is not wrinkled.
 3. The web transport apparatusaccording to claim 2, wherein the image analyzing means detects thelinear pattern of the waveform in the image on the basis of a color orbrightness of the image, and determines the direction of the linearpattern as the entering direction on the basis of a predeterminedcoordinate system.
 4. The web transport apparatus according to claim 2,further comprising: a dancer roller arranged as one of the rollers,applying a tension to the web; tension measuring means for measuring thetension applied by the dancer roller; and tension adjusting means formoving the dancer roller to adjust the tension on the web, wherein thecontroller further comprising: critical tension calculating means forcalculating a critical minimum tension on the web in which the web slipsand a critical maximum tension on the web in which the web is wrinkled,on the basis of a driving information as to a predetermined drivingcondition and of a physical property of the web; and tension controlmeans for controlling the tension adjusting means such that the tensionmeasured by the tension measuring means is within the critical minimumtension and the critical maximum tension.
 5. A web transporting methodfor a web transport apparatus provided with multiple rollerstransporting a sheet web, the method comprising: a critical tensioncalculation step of calculating a critical minimum tension on the web inwhich the web slips and a critical maximum tension on the web in whichthe web is wrinkled, on the basis of a driving information as to apredetermined driving condition of the web transport apparatus and of aphysical property of the web; a tension control step of controlling thetension on the web such that the tension is within the critical minimumtension and the critical maximum tension; an image analysis step ofdetecting a linear pattern of a waveform generated on the web from animage picked up in the web being transported on an angle adjustableroller that is adjustable in a shaft direction and analyzing an enteringdirection of the linear pattern into the shaft of the angle adjustableroller; a shaft angle control step of moving the shaft of the angleadjustable roller such that the shaft direction is perpendicular to theentering direction of the linear pattern analyzed in the image analysisstep.
 6. A web transport control program for a web transport apparatusprovided with multiple rollers transporting a sheet web, the programordering a computer to perform functions of: calculating a criticalminimum tension on the web in which the web slips and a critical maximumtension on the web in which the web is wrinkled, on the basis of adriving information as to a predetermined driving condition of the webtransport apparatus and of a physical property of the web; controllingthe tension on the web such that the tension is within the criticalminimum tension and the critical maximum tension; detecting a linearpattern of a waveform generated on the web from an image picked up inthe web being transported on an angle adjustable roller that isadjustable in a shaft direction and analyzing an entering direction ofthe linear pattern into the shaft of the angle adjustable roller; andmoving the shaft of the angle adjustable roller such that the shaftdirection is perpendicular to the entering direction of the analyzedlinear pattern.